The prior art reveals several methods by which blood or other fluids can be withdrawn and returned to the body. First, the conventional way employs two separate needles, as in U.S. Pat. No. 2,625,932 or two adjoining tubes, as in U.S. Pat. No. 4,098,275. When employing this technique, the two needles must be spaced apart a sufficient distance so as to prevent the cleansed blood from reentering the blood outlet needle and returning to the dialysis machine, but must be sufficiently close to each other to prevent the vein or fistula from collapsing. The prior art also discloses various methods for single-needle dialysis. Examples of this method may be found in U.S. Pat. Nos. 3,756,234 and 3,830,234. However, single-needle dialysis requires operation within only limited flow rates, and further requires that blood be both extracted and returned through the same needle, leaving this procedure not suitable for all patients. A third known manner employs a double lumen catheter to gain the advantage of a conventional two-needle system while requiring only one puncture.
While the use of a double lumen catheter as exhibited by U.S. Pat. No. 4,134,402, has been an advance over the conventional manner of performing dialysis, the problems of recycling, clotting, special equipment requirements, and inadequate flow rates remain. Accordingly, it is the primary object of the present invention to provide an improved catheter capable of eliminating the potential for aeration or clotting of blood as well as increasing the blood flow potential over other double lumen designs.
Other objects and advantages of the invention will become apparent on reading the following detailed description and upon reference to the attached drawings.